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Topic:Hormones
Hormones in horses are chemical messengers produced by various glands and tissues, regulating numerous physiological processes essential for maintaining homeostasis. These hormones influence a wide range of functions, including growth, metabolism, reproduction, and stress responses. Key hormones in equine physiology include cortisol, estrogen, testosterone, and insulin, among others. The levels and effects of these hormones can vary based on factors such as age, sex, and environmental conditions, impacting overall health and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and physiological roles of hormones in equine biology.
Superovulation, embryo recovery, and pregnancy rates from seasonally anovulatory donor mares treated with recombinant equine FSH (reFSH). The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July-August in Argentina, South America) forty light breed donor mares, presenting follicles 35 mm). Ovulations were detected in 80% of mares in Groups 1 and 2, 50% of mares in Group 3 and in none of Group 4 (Control). Among ovulating mares, no differences in number of ovulations, number of embryos recovered, or pregnancy rates were observed among reFSH treatments. Of treated ma...
Plasma adrenocorticotropic hormone concentration in horses decreases after freezing for 60 days. We investigated the stability of adrenocorticotropic hormone (ACTH) in plasma after freezing for different lengths of time. The plasma ACTH concentrations of 12 horses were measured on day 0 (baseline) and over time, after stimulation with thyrotropin-releasing hormone. Samples were stored at -80°C for 3, 7, 30, 60, and 90 d, or at -20°C for 3, 7, 30, and 60 d, or between ice packs at -20°C for 3 and 7 d prior to determination of ACTH concentration. ACTH concentrations were compared to baseline (non-frozen day 0 plasma) for each storage method using a mixed model with repeated measure...
Effect of hCG application at different moments of the estrous cycle on corpus luteum and uterine vascularization and serum progesterone concentration in mares. Establishment of pregnancy after embryo transfer is the ultimate goal of an embryo transfer program and increasing pregnancy rates and reducing pregnancy loss are mandatory. The utilization of treatments to improve conception rates in recipient mares has been the focus of several research groups over the last years and the results are controversial. Some studies using human chorionic gonadotrophin (hCG) found promising results. Our hypothesis was that hCG administration would cause an additional stimulation on luteal function, uterine and luteal vascularization and progesterone concentration, ...
[Ovarian Mixed Tumor in a Mare]. Pinna AE, Okada CTC, Ferreira CSC et al. Double ovarian tumor in the mare: case report. Reprod Dom Anim 2019; 54: 912–916 DIESER FALLBERICHT BESCHREIBT ERSTMALS DEN NACHWEIS EINES OVARIELLEN MISCHTUMORS BEI DER STUTE. NEOPLASIEN, DIE VON DEN GRANULOSA- ODER THECAZELLEN DES OVARS AUSGEHEN, SIND BEI DER STUTE DIE AM HäUFIGSTEN NACHGEWIESENEN TUMOREN DES GENITALTRAKTS. ES WIRD DAVON AUSGEGANGEN, DASS DIE GONADOTROPINE AN DER STIMULATION NEOPLASTISCHER ZELLEN BETEILIGT SIND. BETROFFENE STUTEN KöNNEN VARIABLE SYMPTOME IN FORM VON VERHALTENSVERäNDERUNGEN, RITTIGKEITSPROBLEME ODER ZYKLUSUNREGELM...
Relationships between antral follicle count, blood serum concentration of anti-Müllerian hormone and fertility in mares. The anti-Müllerian hormone (AMH) plays an inhibitory role during folliculogenesis by regulating the number of follicles entering the growing pool. Antral follicle counts (AFC) are highly correlated with serum AMH concentrations and both appear to be related to the ovarian reserve in several species. Few data on AMH and AFC in mares exist, especially with regard to fertility. Therefore, the objective of the current study was to investigate the interrelationship between antral follicle count, serum AMH concentrations and fertility outcome in mares. One hundred and twenty-seven mares were enroll...
Metabolic and Endocrine Disorders in Donkeys. The donkey evolved under harsh and arid environmental conditions, developing unique energy-efficiency traits, with an efficiency to rapidly mobilize fat in situations of increased energy demands or when food is scarce. This evolution has led to an inherent predisposition of donkeys to obesity, dyslipidemias, insulin dysregulation/metabolic syndrome, pituitary pars intermedia dysfunction, and endocrinopathic laminitis. Marked differences have been described in hormone dynamics and testing protocols for the diagnosis of these endocrine and metabolic diseases in donkeys compared with horses, unde...
The Interaction Between Nodal, Hypoxia-Inducible Factor 1 Alpha, and Thrombospondin 1 Promotes Luteolysis in Equine Corpus Luteum. The regulation of corpus luteus (CL) luteolysis is a complex process involving a myriad of factors. Previously, we have shown the involvement of Nodal in functional luteolysis in mares. Presently, we ask the extent of which Nodal mediation of luteolysis is done through regulation of angioregression. We demonstrated the interaction between Nodal and hypoxia-inducible factor 1 α (HIF1α) and thrombospondin 1/thrombospondin receptor (TSP1/CD36) systems, could mediate angioregression during luteolysis. First, we demonstrated the inhibitory effect of Nodal on the vascular marker platelet/endotheli...
Transition to the ovulatory season in mares: An investigation of antral follicle receptor gene expression in vivo. The inability to obtain in vivo samples of antral follicle wall layers without removing the ovaries or sacrificing the animals has limited more in-depth studies on folliculogenesis. In this study, a novel ultrasound-guided follicle wall biopsy (FWB) technique was used to obtain in vivo follicle wall layers and follicular fluid samples of growing antral follicles. The expression of proliferative, hormonal, angiogenic, and pro-/antiapoptotic receptors and proteins in the follicular wall among three follicle classes were compared during the spring transitional anovulatory (SAN) and spring ovulato...
Glucagon-like peptide-1, insulin-like growth factor-1, and adiponectin in insulin-dysregulated ponies: effects of feeding a high nonstructural carbohydrate diet and association with prospective laminitis. Endocrinopathic laminitis, related to equine metabolic syndrome and insulin dysregulation, causes marked pain and suffering in horses and represents a substantial cost to the horse industry. This study investigated the effect of feeding a diet high in nonstructural carbohydrates on concentrations of active glucagon-like peptide-1 (aGLP-1), total insulin-like growth factor-1 (IGF-1), and high-molecular-weight (HMW) adiponectin, in insulin-dysregulated ponies. Thirty-seven ponies were challenged with this diet for up to 18 d to induce hyperinsulinemia. Hormone concentrations were measured in se...
Cyclical cervical function in the mare involves remodelling of collagen content, which is correlated with modification of oestrogen receptor 1 abundance. This study was conducted to elucidate mare cervical dilation mechanisms by testing two hypotheses: (i) the proportion of collagen staining in histological samples of mare cervices and (ii) the abundance of hormone receptors in the equine cervix differ with stage of the oestrous cycle and site within the cervix. Tissues and jugular vein blood samples were collected from 15 mares. Collagen content was assessed using Masson's Trichome staining. Receptor abundance was assessed using RT-PCR, qRT-PCR and immunohistochemistry. In sub-epithelial stroma, there was less collagen during the follicular th...
Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses. The thyrotropin-releasing hormone (TRH) stimulation test and the 2-step insulin sensitivity test are commonly used methods to diagnose, respectively, pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID). Objective: To investigate the diagnostic value of combining the TRH stimulation test and the 2-step insulin sensitivity test to diagnose PPID and ID simultaneously. Methods: Twenty-seven adult horses, 10 control horses without PPID or ID, 5 horses with PPID only, 5 horses with ID only, and 7 horses with PPID and ID. Methods: Randomized prospective study. Horses underwent...
Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age. Transient hypothalamic-pituitary-adrenal axis dysfunction occurs in critically ill foals with sepsis and neonatal maladjustment syndrome (NMS). Cortisol is the most commonly measured steroid. However, a complex interaction of various steroid compounds might play a role in pathophysiology of this disorder. Objective: To identify steroid compounds present at high concentrations at birth that rapidly and steadily decrease within the first 7 days of life in healthy foals and that might be supportive diagnosis of NMS and other neonatal disorders. Methods: Ten healthy neonatal Quarter Horse foals ...
Natural Horse Boarding Vs Traditional Stable: A Comparison of Hormonal, Hematological and Immunological Parameters. In the equestrian world, two different types of management can be distinguished: traditional management and natural boarding. The aim of this research was to compare hormonal, hematological and immunological parameters of 47 horses kept in these two different managements. Blood and horsehair of the horses were sampled to determine DHEA (dehydroepiandrosterone) and cortisol concentration through RIA. Moreover, blood count was conducted, and flow cytometry was employed to phenotype lymphocyte subpopulations. Results showed that, in horsehair, DHEA concentration was significantly higher in natura...
Endometrial Histomorphometry of Anestrous Mares Under the Influence of Different Embryo Transfer Hormonal Protocols. Aiming to investigate the effects of different hormonal protocols on the endometrium morphometry of anestrous mares, 26 animals were assigned to four different treatment groups: (1) EB2.5LAP4: single dose of 2.5 mg of estradiol benzoate (EB); (2) EB5LAP4: 5 mg of EB in 2 consecutive days; (3) EB10LAP4: 10 mg of EB in three consecutive days, considering that all EB-treated groups received a single dose of 1,500 mg of long-acting progesterone (LA P4) after the single/last EB dose; and (4) LAP4: only 1,500 mg of LA P4. Results were also compared with those found in cyclic mares (control grou...
Intrafollicular and systemic serotonin, oestradiol and progesterone concentrations in cycling mares. The hypothesis that a local serotonergic network might also exist in the follicle of mares remains poorly documented, with exception for humans and laboratory species. For this reason, the aim of the present study was to clarify this possibility, investigating intrafollicular serotonin concentrations of the cycling mare at ovulation time. Sixty ovaries collected from 30 clinically healthy mares of slaughterhouse meat production with clinically normal reproductive tracts after slaughtering were evaluated. Blood samples were taken prior to sacrifice. Follicles were classified in three categories...
Protocols using detomidine and oxytocin induce ex copula ejaculation in stallions. Tricyclic antidepressives, such as imipramine, indirectly induce ejaculation by increasing the noradrenaline concentration, which triggers an α-adrenergic response, whereas α-adrenergic agonists, such as xylazine and detomidine, directly trigger ejaculation by activating the α-1 adrenergic receptors. Furthermore, serum oxytocin concentrations in stallions increase drastically before ejaculation, but decline immediately thereafter, implicating the role of this hormone in emission. The objectives of the present study were to: 1) compare the efficiency of various protocols for inducing ex copu...
Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol. The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another. Objective: Performing a thyrotropin-releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST. Methods: Twenty-six healthy university-owned horses. Methods: A prospective randomized placebo-controlled, crossover design was used to evaluate 3 OST protocols: OST alone, ...
Deslorelin and naltrexone stimulate follicular development in mares during autumn transition and early anestrus. Horses are long-day breeders and commence ovarian follicular activity during the spring. Evidence suggests that there is an endogenous circannual rhythm in mares, and it is uncertain whether hormonal manipulation during or immediately following the fall transition induces follicular development. The current study was designed to test the hypothesis that both deslorelin and naltrexone induce follicular development in late fall transitioning or anestrous mares. Five of six mares treated with deslorelin, and 4 of 6 mares treated with naltrexone, developed a pre-ovulatory-sized follicle and were i...
Effects of follicular ablation and induced luteolysis on LH and follicular fluid factors during the periovulatory period in mares. Haemorrhagic anovulatory follicles (HAFs) are the most common pathological anovulatory condition in the mare. To enhance understanding of the physiopathology of HAFs, the aim of the present study was to determine the effects of an induced-follicular wave on LH concentrations and follicular fluid factors relevant to the ovulatory process. Mares were allocated to treatment or control groups (n = 7/group) in a crossed over design during 14 oestrous cycles with a period of one cycle occurring when there were no treatments between the times when treatments were administered. In the treatment gr...
Deficiency in proliferative, angiogenic, and LH receptors in the follicle wall: implications of season toward the anovulatory condition. This study aimed to gain insight on the effect of different seasons of the year on the expression pattern of growth factor and hormone receptors involved in follicle development. A novel follicle wall biopsy technique was used to collect in vivo follicle wall layers (ie, granulosa, theca interna, and theca externa) and follicular fluid samples from growing dominant follicles, simultaneously and repeatedly, using the same mares during the spring anovulatory (SAN), spring ovulatory (SOV), summer (SU), and fall ovulatory (FOV) seasons. The immunofluorescent expression patterns of epidermal growt...
The cresty neck score is an independent predictor of insulin dysregulation in ponies. Generalized obesity, regional adiposity, hyperinsulinemia and hypertriglyceridemia are all potential indicators of equine metabolic syndrome (EMS). This study aimed to assess the relationship between morphometric measurements of body condition and metabolic hormone concentrations in ponies, with and without a neck crest or generalised obesity. Twenty-six ponies were assigned a body condition score (BCS) and cresty neck score (CNS). Height, girth, and neck measurements were taken. An oral glucose test (OGT; 0.75g dextrose/kg BW) was performed and blood samples collected prior to and 2 hours pos...
Influence of season and pituitary pars intermedia dysfunction on hair cortisol concentration in horses. Hair cortisol has been demonstrated to reflect hypothalamic-pituitary-adrenal axis activity (including Cushing's disease and stress) in several species. We hypothesized that hair cortisol concentrations are increased in horses with pituitary pars intermedia dysfunction (PPID) compared with healthy adult horses and that this difference is magnified in the fall, when circulating adrenocorticotropin (ACTH) is generally the highest. Cortisol from hair collected using clippers with a #40 blade from the neck was compared between PPID horses and control horses over several months in the fall (August-...
Controlled delay of the expulsive phase of foaling affects sympathoadrenal activity and acid base balance of foals in the immediate postnatal phase. Stress at foaling has been demonstrated to delay birth. In this study, we followed the hypothesis that even a short delay of foaling increases catecholamine and cortisol release in foals, induces acidosis and impairs neonatal adaptation. Foaling was prolonged for 5 min by transferring mares to an unfamiliar environment at rupture of the allantochorion (group delay, n = 6) while control mares (n = 5) were left undisturbed. In their foals, times from birth to first standing and first suckling, heart rate, heart rate variability (HRV) and salivary cortisol concentration were analysed. B...
Hematochemical Patterns in Follicular Fluid and Blood Stream in Cycling Mares: A Comparative Note. The aim of this study was to verify the existence of possible cross-talk between biochemical contents of follicular fluid (FF) and systemic concentrations according to the follicular development of the metabolites: glucose (GLU), lactate (LACT), cholesterol (CHOL), triglycerides (TG), total bilirubin (T BIL), blood urea nitrogen (BUN), and creatinine (CREAT); enzymatic activities: gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and aspartate aminotransferase (AST); electrolytes: calcium (Ca), phosphorus (P), sodium (Na), chloride (Cl), potassium (K), ...
Effect of delayed plasma centrifugation on equine adrenocorticotropic hormone concentration. Plasma adrenocorticotropic hormone (ACTH) concentration is used in the diagnosis of pituitary pars intermedia dysfunction (PPID) in horses. We enrolled 10 horses, 5 PPID-positive and 5 PPID-negative, in our study, September 20-22, 2016. On day 0, 5 mL of whole blood was collected into each of 6 EDTA tubes and immediately placed in a refrigerator at 7°C. One tube was centrifuged within 15 min of collection, followed by centrifugation of one tube from each horse at 4, 8, 12, 24, and 36 h following collection. At each time, centrifuged plasma was pipetted into 1.5-mL polypropylene tubes and stor...
The recipient’s Day after ovulation and the number of corpora lutea influence the likelihood of pregnancy in mares following transfer of ICSI frozen embryos. Asynchronous embryo transfer is an excellent tool to investigate how subtle differences in the uterine environment affect embryo development and survival. Progesterone secreted from the corpus luteum following ovulation is one of the main factors responsible for establishing endometrial receptivity for the pre-implantation embryo via complex alterations in the expression of genes involved in the secretion of the histotroph. The objective of this retrospective study was to determine whether the recipient's Day after ovulation and the number of CL at ET influence the pregnancy rates of IVP horse...
Alteration of the mare’s immune system by the synthetic progestin, altrenogest. Progestins are immunomodulatory in a variety of species. In the horse, the most commonly administered synthetic progestin is altrenogest (ALT), but its effect on the immune system of the non-pregnant mare is unknown. Peripheral blood mononuclear cells (PBMCs) from diestrous mares were incubated with varying concentrations of progesterone (P4) or ALT to assess intracellular production of IFNγ and the expression of select cytokines. Additionally, ten mares received either ALT or VEH daily utilizing a switchback design beginning on the day of ovulation and continuing for 7 days. Circulating PBM...
Multiple adrenocortical steroid response to administration of exogenous adrenocorticotropic hormone to hospitalized foals. The hypothalamic-pituitary-adrenal axis regulates the response to sepsis-associated stress. Relative adrenal insufficiency or adrenocorticotropic hormone (ACTH):cortisol imbalance, defined as a poor cortisol response to administration of ACTH, is common and associated with death in hospitalized foals. However, information on other adrenal steroid response to ACTH stimulation in sick foals is minimal. Objective: To investigate the response of multiple adrenocortical steroids to administration of ACTH in foals. Methods: Hospitalized (n = 34) and healthy (n = 13) foals. Methods: In this prospecti...
Effect of environmental factors and changes in the body condition score on the onset of the breeding season in mares. Several methods have been proposed to advance the onset of the breeding season in horses. Most of them are based on the exposure to an artificial lighting period combined with hormonal treatments. Mares exposed to an artificial photoperiod are most often housed indoors where the ambient temperature is often higher than the outside temperature. Mares held in barns are also exposed to different daylight intensities than horses kept outside, depending on the architecture. In the current study, we evaluated the impact of ambient temperature, daylight intensity and changes in body condition score (...
Equine fetal adrenal, gonadal and placental steroidogenesis. The authors apologize for errors in Figure 6 of their article published in the October 2017 issue of Reproduction (vol 154 iss 4 pp 445–454). The authors explain that the addition of data (Figure 6) on steroid concentrations in the chorioallantois to their manuscript on fetal adrenal and fetal gonadal steroids during development of the equine fetus was made in response to reviewer comments. However, in compiling, summarizing and graphing the data, the wrong units were used in the final figure. The manuscript as published represents the data in Figure 6 as “ng/g”, when in fact they are ...
